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   <title>The b Command</title>
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<h1>
b</h1>
<!--INDEX "breakpoint number" brkcmd "b command" -->
<p>The b command sets and displays breakpoints.
<h2>
Format</h2>

<dl> 
  <dd> The format for the b command is:</dd>
  <pre><font size="+1">b

b <i>adr..

</i>b <i>adr</i> -s <i>str</i></font>

where:

</pre>
  <table width="95%">
    <tr bgcolor="#CCCCCC"> 
      <td ALIGN=LEFT VALIGN=TOP WIDTH="74"><i>adr</i></td>
      <td width="695">specifies an address for the breakpoint. Up to 32 breakpoints 
        addresses can be set.&nbsp;</td>
    </tr>
    <tr> 
      <td width="74">-s <i>str</i></td>
      <td width="695">executes the command string when the breakpoint is hit.&nbsp;</td>
    </tr>
  </table>
  <p>Invoking the b command with no options causes the <a href="mondef.htm">Monitor</a> 
    to print a list of the current breakpoints.
</dl>

<h2>
Functional Description</h2>

<dl> 
  <dd> The b command sets a breakpoint at the specified address or addresses. 
    Multiple addresses may be specified. Specified addresses must be word-aligned.</dd>
  <br>
  &nbsp; 
  <p>The <a href="mondef.htm">Monitor</a> automatically assigns a number to each 
    breakpoint. <br>
    The <a href="mondef.htm">Monitor</a> allocates the lowest available breakpoint 
    number from 0 to 31 to any new breakpoint. 
  <p>The <a href="mondef.htm">Monitor</a> reports a new breakpoint's number immediately 
    after the breakpoint is set (see the examples at the end of this subsection 
    for illustration of this). The assigned numbers can be used in the <a href="c_db.htm">db</a> 
    (Delete Breakpoint) command. 
  <p><b>The brkcmd Variable</b> 
  <p>When a breakpoint is reached, the command list specified in the environment 
    variable brkcmd is executed. The default setting for brkcmd is: 
  <pre>brkcmd = "l @pc 1"</pre>
  This command "<tt>l @pc 1</tt>", specifies that when the breakpoint occurs, 
  the <a href="mondef.htm">Monitor</a> will disassemble one line starting at the 
  address of the program counter. 
  <p>You can change the breakpoint command variable with the set command. For 
    example, you can include additional monitor commands in the brkcmd variable. 
    You must separate additional commands on the command line with a semicolon. 
    For example, entering the following command lists one line after reaching 
    a breakpoint, and then displays all the register values. 
  <pre>set brkcmd "l @epc 1;r *"

</pre>
  By default, breakpoints are cleared when the load command is executed. See the 
  section on the load command later in this document for details on how to override 
  automatic breakpoint clearing after a download operation. 
  <p>Some examples illustrating the use of the b command follow. <br>
    &nbsp; 
  <table width="95%">
    <tr bgcolor="#CCCCCC"> 
      <td width="231"><tt>PMON> b a002000c&nbsp;</tt></td>
      <td width="538">Set a breakpoint at 0xa002000c.&nbsp;</td>
    </tr>
    <tr> 
      <td width="231"><tt>Bpt 1 = a002000c&nbsp;</tt></td>
    </tr>
    <tr bgcolor="#CCCCCC"> 
      <td width="231"><tt>PMON> b&nbsp;</tt> <br>
        <tt>Bpt 0 = 8002022c</tt> <br>
        <tt>Bpt 1 = a002000c&nbsp;</tt></td>
      <td VALIGN=TOP width="538">Display all breakpoints.&nbsp;</td>
    </tr>
    <tr> 
      <td VALIGN=TOP width="231"><tt>PMON> b 80021248 -s "r"&nbsp;</tt></td>
      <td width="538">Set a breakpoint at 0x80021248. Display registers when the 
        breakpoint is encountered.&nbsp;</td>
    </tr>
  </table>
</dl>

<h2>
See Also</h2>

<dl>
<dd>
<a href="c_db.htm">db</a> and <a href="c_load.htm">load</a> commands.</dd>
</dl>

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